LXR qemu/crypto/random-platform.c

   1/*
   2 * QEMU Crypto random number provider
   3 *
   4 * Copyright (c) 2015-2016 Red Hat, Inc.
   5 *
   6 * This library is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU Lesser General Public
   8 * License as published by the Free Software Foundation; either
   9 * version 2.1 of the License, or (at your option) any later version.
  10 *
  11 * This library is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 * Lesser General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU Lesser General Public
  17 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18 *
  19 */
  20
  21#include "qemu/osdep.h"
  22
  23#include "crypto/random.h"
  24#include "qapi/error.h"
  25
  26#ifdef _WIN32
  27#include <wincrypt.h>
  28static HCRYPTPROV hCryptProv;
  29#else
  30# ifdef CONFIG_GETRANDOM
  31#  include <sys/random.h>
  32# endif
  33/* This is -1 for getrandom(), or a file handle for /dev/{u,}random.  */
  34static int fd;
  35#endif
  36
  37int qcrypto_random_init(Error **errp)
  38{
  39#ifdef _WIN32
  40    if (!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,
  41                             CRYPT_SILENT | CRYPT_VERIFYCONTEXT)) {
  42        error_setg_win32(errp, GetLastError(),
  43                         "Unable to create cryptographic provider");
  44        return -1;
  45    }
  46#else
  47# ifdef CONFIG_GETRANDOM
  48    if (getrandom(NULL, 0, 0) == 0) {
  49        /* Use getrandom() */
  50        fd = -1;
  51        return 0;
  52    }
  53    /* Fall through to /dev/urandom case.  */
  54# endif
  55    fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
  56    if (fd == -1 && errno == ENOENT) {
  57        fd = open("/dev/random", O_RDONLY | O_CLOEXEC);
  58    }
  59    if (fd < 0) {
  60        error_setg_errno(errp, errno, "No /dev/urandom or /dev/random");
  61        return -1;
  62    }
  63#endif
  64    return 0;
  65}
  66
  67int qcrypto_random_bytes(void *buf,
  68                         size_t buflen,
  69                         Error **errp)
  70{
  71#ifdef _WIN32
  72    if (!CryptGenRandom(hCryptProv, buflen, buf)) {
  73        error_setg_win32(errp, GetLastError(),
  74                         "Unable to read random bytes");
  75        return -1;
  76    }
  77#else
  78# ifdef CONFIG_GETRANDOM
  79    if (likely(fd < 0)) {
  80        while (1) {
  81            ssize_t got = getrandom(buf, buflen, 0);
  82            if (likely(got == buflen)) {
  83                return 0;
  84            }
  85            if (got >= 0) {
  86                buflen -= got;
  87                buf += got;
  88            } else if (errno != EINTR) {
  89                error_setg_errno(errp, errno, "getrandom");
  90                return -1;
  91            }
  92        }
  93    }
  94    /* Fall through to /dev/urandom case.  */
  95# endif
  96    while (1) {
  97        ssize_t got = read(fd, buf, buflen);
  98        if (likely(got == buflen)) {
  99            return 0;
 100        }
 101        if (got > 0) {
 102            buflen -= got;
 103            buf += got;
 104        } else if (got == 0) {
 105            error_setg(errp, "Unexpected EOF reading random bytes");
 106            return -1;
 107        } else if (errno != EINTR) {
 108            error_setg_errno(errp, errno, "Unable to read random bytes");
 109            return -1;
 110        }
 111    }
 112#endif
 113    return 0;
 114}
 115